In the prior art, a unit composed of a combination of an internal combustion engine with an electric motor, a unit using an electric motor as a prime mover and so on are known as a power unit of a vehicle. In order to control a drive torque and speeds of the internal combustion engine and the electric motor, a transmission is employed in a vehicle having the power unit of those kinds. One example is disclosed in Japanese Patent Laid-Open No. 2003-127681. The system disclosed in Japanese Patent Laid-Open No. 2003-127681 is a hybrid vehicle drive system in which an internal combustion engine is connected with a carrier of a planetary gear mechanism, and a first motor/generator is connected with a sun gear of the planetary gear mechanism. Also, a ring gear is connected with a member of an input side of a geared automatic transmission. A member of an output side of the automatic transmission is connected with a propeller shaft, and a second motor/generator is connected with the propeller shaft. Thus, according to the system taught by Japanese Patent Laid-Open No. 2003-127681, the planetary gear mechanism functions as a distribution mechanism distributing an engine power to the first motor/generator and to the automatic transmission. A torque is added or absorbed by a second motor/generator in the process of transmitting the power from the distribution mechanism to the automatic transmission. Japanese Patent Laid-Open No. 2003-127681 also discloses a configuration in which the second motor/generator is connected to an input side of the automatic transmission, and the output member of the automatic transmission is connected with the propeller shaft through a gear train.
According to the unit disclosed in Japanese Patent Laid-Open No. 2003-127681, the second motor/generator is connected with the propeller shaft through a gear pair, or connected with the automatic transmission. Specifically, a rotor is fixed to a rotary shaft of a predetermined gear of the gear pair, or to an input shaft of the automatic transmission. According to the unit of Japanese Patent Laid-Open No. 2003-127681, therefore, the second motor/generator is connected with the gear pair or with the automatic transmission when assembled. For this reason, in case of carrying out an inspection such as a torque measuring of the second motor/generator or carrying out some sort of adjustment before completion of assembling of an entire unit, the gear pair and the automatic transmission also have to be rotated. As a result, measurement accuracy and accuracy of adjustment of rotation angle may be deteriorated by torques of the gear pair and the automatic transmission.